Various conventional techniques related to small watercrafts have been known.
The small watercrafts include a small watercraft for leisure use that is used for sports, recreations, and the like (see Patent Literature 1).
For example, a small watercraft is mainly made of an FRP (Fiber Reinforced Plastics) material, and has an overall length of approximately 12 m, a weight of approximately 10 tons, and a complement of 12 persons.
Some small watercrafts are configured to obtain thrust by driving a propeller with an engine serving as a power source, and to introduce intake air for the engine into an engine room in an inboard section from the outside through air intake ports.